A PEX5 missense allele preferentially disrupts PTS1 cargo import into Arabidopsis peroxisomes

Abstract

The sorting of eukaryotic proteins to various organellar destinations requires receptors that recognize cargo protein targeting signals and facilitate transport into the organelle. One such receptor is the peroxin PEX 5, which recruits cytosolic cargo carrying a peroxisome‐targeting signal ( PTS ) type 1 ( PTS 1) for delivery into the peroxisomal lumen (matrix). In plants and mammals, PEX 5 is also indirectly required for peroxisomal import of proteins carrying a PTS 2 signal because PEX 5 binds the PTS 2 receptor, bringing the associated PTS 2 cargo to the peroxisome along with PTS 1 cargo. Despite PEX 5 being the PTS 1 cargo receptor, previously identified Arabidopsis pex5 mutants display either impairment of both PTS 1 and PTS 2 import or defects only in PTS 2 import. Here, we report the first Arabidopsis pex5 mutant with an exclusive PTS 1 import defect. In addition to markedly diminished GFP ‐ PTS 1 import and decreased pex5‐2 protein accumulation, this pex5‐2 mutant shows typical peroxisome‐related defects, including inefficient β‐oxidation and reduced growth. Growth at reduced or elevated temperatures ameliorated or exacerbated pex5‐2 peroxisome‐related defects, respectively, without markedly changing pex5‐2 protein levels. In contrast to the diminished PTS 1 import, PTS 2 processing was only slightly impaired and PTS 2‐ GFP import appeared normal in pex5‐2 . This finding suggests that even minor peroxisomal localization of the PTS 1 protein DEG 15, the PTS 2‐processing protease, is sufficient to maintain robust PTS 2 processing.

Essential Roles of the Linker Sequence Between Tetratricopeptide Repeat Motifs of Ethylene Overproduction 1 in Ethylene Biosynthesis

“…For example, seven TPR motifs of PEX5 form an antiparallel helix-turn-helix unit and have a role in the recognition and binding of the C-terminal "SKL" tripeptides, or variants thereof, of ligand proteins (Sampathkumar et al, 2008). Similarly, the mutation of glycine 8 in PEX5 can disrupt its ligand recognition ability (Patel et al, 2019). This indicates a potentially similar TPR structure formation between ETO1 and PEX5.…”

PEX16 contributions to peroxisome import and metabolism revealed by viable Arabidopsis pex16 mutants

“…Despite displaying more severe peroxisome‐related physiological defects than pex16‐2 , pex16‐1 had a less pronounced PTS2‐processing defect than pex16‐2 (Figures B, 7C). This difference in PTS2 processing hints that the pex16‐2 lesion might preferentially disrupt PTS2 import (Patel et al ). However, we detected similar GFP‐PTS1 and PTS2‐GFP import defects in pex16‐1 and pex16‐2 (Figure A).…”